This can be a hassle to some players. So, ...
How? -- Please elaborate.
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For example, I'm guessing, you are hunting the last missing piece among the 9 pieces of eight... No, nine of nine...
My guessing is totally logical (reasonable) because it looks as if you want to know whether you have got a BP from aiding and if you do, it seems, that you will stop aiding more? -- Now, if it was not the last piece, surely you will continue hunting for it.
In which case, I vote -1 and propose a BeTtEr alternative...
The FiReWoRks! -- that splash above the town hall, whenever the player enters a new age -- they should use those more often.
When the player has collected a full set of BP, fireworks should be lighted up on top the corresponding Great Building, and a big banner that follows saying "congratulations! You've collected a full set of blueprints!"